Gas-cooled electro-magnetic stirrer



Aug. 10, 1965 G. KARLSSON ETAL 3,199,842

GAS-COOLED ELECTRO-MAGNETIC STIRRER Filed April 4. 1963 2 Sheets-Sheet 2 BYgoihaj/f & M

ATTORNEYS United States Patent s,1ss,s42 GAS-COOLED ELECTRO-MAGNETIC STIRRER Gtista Karlsson, Kare Folgei'ii, Mats Rydinger, and Thor Theleniarck, Vasteras, Sweden, assignors to Alhnanna Svenska Elelitrisha Ahtieholaget, Vasteras, Sweden, 2 Swedish corporation Filed Apr. 4, 1963, Ser. No. 270,714 Claims priority, application Sweden, Apr. 12, 1962, 4,067/ 62 Claims. (Cl. 259-1) The present invention relates to gas-cooled, for example, air-cooled, electro-magnetic stirrers for metallurgical furnaces.

An advantage with air-cooling of electro-magnetic stirrers is that the cooling system with accessories such as fans, etc., may be firmly attached to the stirrer and accompany it later during tipping, together with the furnace, without being hindered by cooling medium tubes or tube connections and the like. A direct air cooling of an electro-magnetic stirrer is feasible, but in this case air must be taken from the immediate surroundings of the stirrer and the oven, which latter as a rule is extremely dust-laden and dirty. This would result in blocking of the cooling channels, faulty insulation, etc., and therefore such direct cooling must be considered unsuitable unless special cooling air cleaning arrangements are made, which are expensive and work-demanding because of the need for frequent filter changes and the like.

The invention gives a solution, among other things of the dirt problem for windings, and at the same time utilizes the advantages of the air cooling and is characterised in that cooling medium, for example air, is arranged to circulate in a closed inner path, inter alia in heat conducting contact with the winding and laminated iron core of the stirrer and via a heat exchanger, through which is also arranged separately from said path means for the transport of supplied cooling gas, e.g. air. In this Way the closed cooling path (the inner system) is kept clean, whereas the cooling gas taken from the outside may consist of the dust-laden air around the furnace and the stirrer. The cooling paths for the last-mentioned gas (the outer system) are separated from the winding, sheet core, etc., and may be made easily cleanable, which for example may be the case for the heat exchanger, which may be made with channels, alternately belonging to the closed cooling path and the path for the cooling gas from the outside, which channels may be closed by a common cover detachable for rinsing and cleansing of the channels. Said cooling system is tiltable together with the stirrer. For each cooling medium or cooling gas path respectively is arranged at least one fan (or pump in the.outer path for fluid cooling medium).

As cooling medium in the closed path, air or nitrogen or other non-explosive gas may in the first case be used. As cooling medium in the other cooling system air, nitrogen, or othere non-explosive gas may be used. With the use of any other gas than air this system should thus also be made closed. Fluid cooling mediums could also be used in this outer system. c

The invention is defined in more detail in the accompanying figures, of which FIGURE 1 shows in sect-ion a part of an electric arc furnace and the stirrer with cooling means. FIGURE 2 shows a section along the line A-A in FIGURE 1. FTGURES 3 and 4 show different parts of the heat exchanger, belonging to the outer and inner cooling systems respectively. FIGURE 5 is a cross-section substantially on the line 5-5 of FIG- URE 1.

In FIGURES l and 2 is shown an electric arc furnace 11 or ladle charged with a steel or iron melt, possibly vacuum encased. Under the bottom of this is placed a stirrer 12 with straight core legs. Along the surfaces facing the furnace are placed a ceramic protective layer 13 of known kind. Under this is placed coil sides 14 spaced from part 13 by spacers 14' and with a space 15 between them and the protective layer for a cooling medium (air, nitrogen, etc.). Under the coil sides 14 is placed the laminated sheet core 16 with a space 17 between it and the coil sides 14 for a cooling medium. The coil ends (18, FIGURE 2) should also be cooled in the same way as the coil sides, and here paths 2% for cooling medium enclose them. Said spaces 15, 17 and 29 are in a closed cooling system (the inner system),

which also includes channels 19 outside of the windings and sheet core and channels 28 in heat exchanger 20. The circulation of cooling medium in said inner cooling system is produced by means of one or more fans 21. As is evident from the above no substantial fouling or other dust coating of the winding 14, sheet core 16, spaces 15, 17, 28, 29 or channels 19, will occur from the cooling medium in the inner system because of its closed character. It may be possible however with regard to the demand for freedom from dust in the system to supply cooling medium to a certain extent from outside, for example by conduits from a dust-free place (not shown).

The outer cooling may occur by means of cooling gas, in the case shown and on the whole simplest by means of air. It is possible also for this purpose to use the dustfilled air around the furnace 11 and the stirrer 1-2. At 22 air is pumped in by means of one or more fans 23 through the heat exchanger 20 and out at 25. Channels 27 in the heat exchanger 20, belonging to the outer c0oling system, are provided with a common cover 26 or the like, detachable for cleansing of the channels. The heat conducting contact between the channels in the different systems inside the heat exchanger 20 (27 to the outer, 23 to the inner system) will be good for effecting cooling down of the cooling medium in the inner, closed cooling system from the air in the outer. With fluid cooling medium in the outer cooling system pumps are used instead.

In FIGURE 3 is shown in section a part-channel, belonging to the outer cooling system inside the heat exchanger 2l with inlet at 23 and outlet at 25. FIGURE 4 shows a part-channel inside the heat exchanger for the inner, closed cooling system with the arrow showing the through path for the cooling medium. As is evident from FIGURE 2 the part-channels are oblong and upended beside each other in order to attain effective heat transmission between the systems (27 to 28). The circulation paths in the two systems are evident from the arrows in FIGURES 1 and 5 The heat exchanger may of course be made in many ways known in the art. The construction of channels and fans and their positioning may also be varied in many ways, within the scope of the following claims.

\Ve claim:

1. Gas-cooled electro-magnetic stirrer for metallurgical furnaces, said stirrer having windings and a sheet iron core, said stirrer comprising means forming a closed inner circulation path for cooling gas, a heat exchanger positioned on the opposite side of the stirrer from the furnace, said heat exchanger including first passages forming a part of said inner circulation path, said path being in heat contact with the windings and sheet iron core of the stirrer, means forming a second path including second passages in said heat exchanger in heatexchange relation with said first passages for guiding cooling gas from outside through said second passages in said heat exchanger, said second passages being separated from said inner path.

2. In a stirrer as claimed in claim 1, said heat exchanger including a removable bottom closing all of said passages.

3. Gas-cooled electro magnetic stirrer for metallurgical furnaces having windings and a sheet iron core, said stirrer having a wall facing the furnace bottom, said windings being located below, and spaced from said wall and said sheet iron core being located below, and spaced from the said windings, said stirrer comprising means forming a closed inner circulation path for cooling gas, said path including the spaces above and below the windings, a heat exchanger positioned below the core, said heat exchanger including first passages forming a part of said inner circulation path, means forming a second path including second passages in said heat exchanger in heat exchange relation with said first passages for guiding cooling gas from outside through said sec- 0nd passages, said second passages being separated from the first passages of the heat exchanger.

4. In a stirrer as claimed in claim 3, means for positively circulating gas through each of said paths.

5. In a stirrer as claimed in claim 3, said heat exchanger including a removable bottom closing all of the said passages.

References Cited by the Examiner UNITED STATES PATENTS 24,462 4/58 Dreyfus 1326 2,652,441 9/53 Gynt et a1. 1326 2,835,717 5/58 Fredriksson 13-26 2,960,556 11/60 Fredriksson 13-26 CHARLES A. WILLMUTH, Primary Examiner. 

1. GAS-COOLED ELECTRO-MAGNETIC STIRRER FOR METALLURGICAL FURNACES, SAID STIRRER HAVING WINDINGS AND A SHEET IRON CORE, SAID STIRRER COMPRISING MEANS FORMING A CLOSED INNER CIRCULATION PATH FOR COOLING GAS, A HEAT EXCHANGER POSITIONED ON THE OPPOSITE SIDE OF THE STIRRER FROM THE FURNACE, SAID HEAT EXCHANGER INCLUDING FIRST PASSAGES FORMING A PART OF SAID INNER CIRCULATION PATH, SAID PATH BEING IN HEAT CONTACT WITH THE WINDINGS AND SHEET IRON CORE OF THE STIRRER, MEANS FORMING A SECOND PATH INCLUDING SECOND PASSAGES IN SAID HEAT EXCHANGER IN HEATEXCHANGE RELATION WITH SAID FIRST PASSAGES FOR GUIDING COOLING GAS FROM OUTSIDE THROUGH SAID SECOND PASSAGES IN SAID HEAT EXCHANGER, SAID SECOND PASSAGES BEING SEPARATED FROM SAID INNER PATH. 